In the manufacture of electric motors, a basic requirement for high efficiency and low noise is that the air gap between the rotor and stator be maintained within predetermined limits. However, assembly methods for motors often are such that the tolerances do not assure a precise final construction of the motor.
Further in certain types of motors such as used for ceiling fans, it is required to have a conduit extending through the rotating shaft of the motor in order that wiring may be provided to controls and light fixtures suspended from the motor. In such electric motors, a common problem is that of having satisfactory bearings which will provide long life with minimum maintenance. Thus, it has been common to utilize ball or roller bearings which are effective but costly.
Among the objectives of the present invention are to provide an electric motor having a novel bearing system which incorporates lubricating means for effectively lubricating the bearings without leakage or loss of oil; which utilizes a minimum number of parts and which can be manufactured readily and requires minimum maintenance.
In accordance with the invention, the electric motor comprises a lower housing, and an upper housing. The lower housing comprises a hollow stationary shaft, a stator mounted on the shaft. The upper housing comprises a tube rotatably mounted on the shaft, a rotor fixed on the tube and surrounding said stator for rotation about the shaft. A thrust bearing is provided between the end of the tube and the lower housing, longitudinally upper and lower spaced bearings are provided between the tube and the hollow shaft. An oil holding element is interposed between the bearings. An oil sump is provided in the lower housing associated with the lower bearing such that oil flowing out of the holding element collect in the oil sump.